Ion-based triple sensor

ABSTRACT

An ion-based triple sensor is disclosed. The ion-based triple sensor may include an ion sensing unit, configured to measure an ionic current intensity, a pressure sensing unit, configured to measure a pressure, and a temperature sensing unit, configured to measure a temperature. The ion-based triple sensor may further include a signal processing unit coupled to the ion sensing unit, the pressure sensing unit and the temperature sensing unit. The signal processing unit may include a filtering component, configured to filter at least one of the ion, pressure and temperature measurements, and a data acquisition component, configured to sample the filtered measurements and communicate the samples to a controller.

RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 11/984,487, filed on Nov. 19, 2007, to ION-BASED TRIPLE SENSOR,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This application relates to a sensor, and more particularly, to anion-based triple sensor.

BACKGROUND

In a combustion chamber of a diesel engine as well as aftertreatmentcomponents, malfunctions of the air inlet valve, exhaust valve, and/orinjector may lead to knock, misfiring, and out-of-phase combustion. Todetect these malfunctions, an engine control module (ECM) usually relieson in-cylinder pressure measurements at particular crank angles. Forexample, pressure measurements may be obtained by a quartz pressuresensor installed in the combustion chamber or aftertreatment components.However, the measured pressure data are reliable only after averagingtens of engine cycles, and thus, result in significant delays in engineand/or aftertreatment component fault detection. The delay prevents theECM from promptly adjusting control parameters to avoid catastrophicevents of engine operation. Therefore, it is desirable that the sensorprovides timely feedback to the ECM as early as the first engine cycle.

Furthermore, a chemical reaction status in the combustion chamber or anaftertreatment component may be indicated by multiple characteristicparameters, such as pressure, temperature, and ion current intensity.Therefore, it may be helpful that a sensor can measure thesecharacteristic parameters at the same location and combine them todetermine the unique chemical reaction condition. In addition, it mayalso be beneficial if the sensor has a self-validation function tomonitor and detect sensor faults using its own measurements.

An apparatus for detecting knock in an internal combustion engine isdescribed in U.S. Pat. No. 6,789,409 to Tanaya et al. (“the '409patent”). The '409 patent describes an apparatus for accuratelydistinguishing knock from normal noise in the internal combustionengine. The apparatus includes an ion-current detection device fordetecting an ion current flowing between the electrodes followingcombustion in the combustion chamber, a knock detection device fordetecting knock occurring following an abnormal rise in either pressureor temperature in the combustion chamber, a center-of-gravitycalculation device for calculating a gravity position of an ion currentwaveform, and a knock determination device for determining knock ornoise based on outputs of the knock detection device and thecenter-of-gravity calculation device.

Although the knock detection apparatus described in the '409 patent maybe effective for detecting knock in the internal combustion engine, itmay be problematic. For example, the knock detection apparatus describedin the '409 patent relies on an abnormal rise in either the steady-statepressure or the steady-state temperature to detect the knock, and thusmay not be capable of providing timely and accurate feedback to the ECMshortly after startup, as the machine has not been operated long enoughfor the temperature or pressure sensor to reach steady-state operation.Furthermore, although the apparatus described in the '409 patentmeasures multiple characteristic parameters (e.g., ion current,pressure/temperature, etc.), these measurements are obtained fromsensors that are located in different parts of the engine. As a result,the apparatus described in the '409 patent may not be able to determinea chemical reaction status corresponding to a single location, as thepressure measurement data may have been gathered from a different partof the engine than the ion current data. In addition, the apparatusdescribed in the '409 patent may lack self-validation functions.

The disclosed ion-based triple sensor is directed towards overcoming oneor more of the shortcomings set forth above.

SUMMARY

In one aspect, an ion-based triple sensor is disclosed. The ion-basedtriple sensor may include an ion sensing unit configured to measure anionic current intensity, a pressure sensing unit configured to measure apressure, and a temperature sensing unit configured to measure atemperature. The ion-based triple sensor may further include a signalprocessing unit coupled to the ion sensing unit, the pressure sensingunit and the temperature sensing unit. The signal processing unit mayinclude a filtering component configured to filter at least one of theion, pressure and temperature measurements, and a data acquisitioncomponent configured to sample the filtered measurements and communicatethe samples to a controller.

In another aspect, an engine diagnostic method is disclosed. The enginediagnostic method may include acquiring an ionic current intensitysignal, a pressure signal and a temperature signal in a combustionchamber of an engine, and determining an inherent response differencebased on the acquired signals. The engine diagnostic method may furtherinclude determining a chemical reaction status in the combustionchamber, based on the inherent response difference. The enginediagnostic method may also include detecting an engine fault if thechemical reaction status is outside of a threshold range.

In yet another aspect, an ion-based triple sensor self-validation methodis disclosed. The ion-based triple sensor self-validation method mayinclude acquiring an ionic current waveform, and calculating at leastone of a transient pressure value and a transient temperature value,based on the ionic current waveform. The ion-based triple sensorself-validation method may further include acquiring at least one of asteady-state pressure signal and a steady-state temperature signal. Theion-based triple sensor self-validation method may also includecomparing the at least one transient value with a correspondingsteady-state measurement, and detecting a fault associated with theion-based triple sensor, if the difference between the transient valueand the corresponding steady-state is outside of a threshold range.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 provides a diagrammatic illustration of an engine combustionsystem, in accordance with an exemplary embodiment of the presentdisclosure;

FIG. 2 provides a diagrammatic illustration of an ion-based triplesensor, in accordance with an exemplary embodiment of the presentdisclosure;

FIG. 3 provides a flowchart of an exemplary combustion fault detectionprocess of an ion-based triple sensor, in accordance with the embodimentof the present disclosure; and

FIG. 4 provides a flowchart of an exemplary combustion fault detectionand self-validation process of an ion-based triple sensor, in accordancewith the embodiment of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 provides a diagrammatic illustration of an engine combustionsystem 10. Engine combustion system 10 may include, among other things,an engine 110, an aftertreatment system 120, an engine control module(ECM) 130, an indication device 140, and at least one ion-based triplesensor 200. Engine 110 may be any type of internal combustion enginesuch as, for example, a gasoline engine, a gaseous fuel-powered engine,or a diesel engine. Engine 110 may include an engine block that at leastpartially defines a plurality of combustion chambers 111. In theillustrated embodiment, engine combustion system 10 includes fourcombustion chambers 111. However, it is contemplated that engine 110 mayinclude a greater or lesser number of combustion chambers 111 than isillustrated in FIG. 1. Furthermore, combustion chambers 111 may bedisposed in any suitable geometric configuration or orientation, suchas, for example, an “in-line” configuration, a “V” configuration, or anyother suitable engine configuration or orientation.

Each combustion chamber 111 may include an air inlet valve, a fuelinjector, and an igniter. The fuel injector may spray fuel intocombustion chamber 111, and the air inlet valve may allow air flow intocombustion chamber 111 to mix with the fuel. The igniter may facilitateignition of the fuel and air mixture during an injection event. Heatgenerated by the fuel combustion results in a sliding motion of eachpiston within the respective combustion chamber 111. During operation ofthe engine described above, a complex mixture of air pollutants isproduced as a byproduct of the combustion process and flows intoaftertreatment system 120 via an exhaust passage 112. Malfunctions ofthe air inlet valve, fuel injector and/or igniter may lead to knock,misfiring, and out-of-phase combustion in combustion chamber 111,potentially resulting in abnormal or inefficient operation of theengine.

The air pollutants flowing out of the exhaust valve are composed ofsolid particulate matter and gaseous compounds which may include, amongother things, nitrous oxides (NOx). Aftertreatment system 120 mayinclude exhaust treatment components, including, a NOx trap, a dieselparticulate trap (DPT), a three-way catalyst converter, an oxidizedcatalyst converter, etc. Chemical reactions, for example, selectivecatalyst reduction, may take place in these components to convert NOxinto environmentally-friendly products, such as nitrogen gas and water.The aftertreatment products may exit the machine via a tailpipe 121.Malfunctions of exhaust components may lead to excessive particulate orgaseous emission discharge. If the emission discharge level exceedslimits established by a regulating body, engine combustion system 10 maybecome non-compliant with the emission regulations.

To facilitate the appropriate operation of engine combustion system 10,sensors may be installed in combustion chambers 111 and aftertreatmentsystem 120 to measure one or more characteristic parameters indicativeof the chemical reaction status. Examples of the characteristicparameter include ion current intensity, pressure, and temperature.

Ion current intensity refers to a current flow generated by the releaseof negatively charged ions resulting from chemical reactions incombustion chambers 111 and/or aftertreatment system 120. For example,because of the high temperatures and pressures that exist withincombustion chambers 111, the combustion reaction often causes negativelycharged ions associated with one or more of the chemicals to bereleased, generating a particular ion current. “Normal” operation of theengine typically exhibits an ion current with particularcharacteristics. By measuring the deviation of an ion current intensityfrom the one indicative of “normal” operation of the engine, amalfunction of an engine combustion process may be detected.

In addition to ion current intensity, temperature and pressuremeasurements associated with the chemical reactions may also be used tocharacterize and identify the status of chemical reactions associatedwith an engine system. For example, engine operation and, morespecifically, engine combustion and aftertreatment status are correlatedwith the temperature and pressure of the chemical reactions used in eachof the combustion and aftertreatment processes.

In fact, particular chemical reaction status information can often bemore definitely and accurately derived from interrelationships betweenion current intensity, pressure, and temperature associated with achemical reaction. For example, “normal” engine operation may becharacterized by a particular “signature” (referred to herein as theinherent response difference) characterized by an ion current intensitylevel at the corresponding temperature and pressure values. Similarly, aplurality of engine malfunctions may also be characterized by a uniquerelationship between ion current intensity, pressure, and temperature.By identifying and characterizing the unique “signatures” associatedwith normal engine operation and different engine operationmalfunctions, problems associated with combustion or aftertreatmentprocesses may be more easily diagnosed and corrected.

By way of example, a malfunction of the spark plug may generate adifferent ion current “signature” than, for example, a problem in theconcentration of the air-fuel mixture. By measuring instantaneouschanges in a local ion current surge, along with pressure andtemperature data corresponding to the ion current surge, problemsassociated with the engine system may be identified. Furthermore, inorder to properly locate and isolate problems in combustion andaftertreatment processes, it may be advantageous to gather the ioncurrent intensity data, pressure data, and temperature data fromprecisely the same location (e.g., the same combustion chamber).

Consistent with the embodiment of the present disclosure, at least oneion-based triple sensor 200 may be installed in the combustion chambers111 and/or aftertreatment system 120. Ion-based triple sensor 200 may beconfigured to measure an ion current intensity signal, a pressuresignal, and a temperature signal, substantially simultaneously and inthe same location. It is also contemplated that ion current intensity,pressure, and temperature may be measured in a non-simultaneous mannersuch as, for example, sequentially and/or periodically, at differenttime intervals.

Ion-based triple sensor 200 may be in communication with an enginecontrol module (ECM) 130 via a communication harness. ECM 130 mayinclude all the components required to run a control application suchas, for example, a memory, a secondary storage device, and a processor,such as a central processing unit. One skilled in the art willappreciate that the ECM 130 may contain additional and/or differentcomponents than those listed above. ECM 130 may be dedicated to thecontrol of engine combustion system 10, or may embody a general machineor power system microprocessor capable of controlling numerous machineor power system functions. ECM 130 may be associated with and/or includevarious other circuits such as, for example, power supply circuitry,signal conditioning circuitry, and solenoid driver circuitry, amongothers.

ECM 130 may be configured to receive the ion current intensity signal,the pressure signal, and the temperature signal and determine a uniquechemical reaction status based on the signals received. According to oneembodiment, ECM 130 may determine an inherent response difference amongthe three signals. The inherent response difference, as the term is usedherein, refers to a combination of the chemical reaction statusindications corresponding to the three signals that define the ioncurrent intensity, pressure, and temperature “signature” associated withthe chemical reaction. For example, one common combustion systemmalfunction, commonly referred to as shock-fault, occurs when theair-fuel mixture in combustion chambers 111 prematurely combusts in thecombustion system. An ion current surge indicative of the shock faultmay be detected by ion-based triple sensor 200. Meanwhile, pressure andtemperature may also be measured. ECM 130 may combine these indicationsand map the inherent response difference to a unique status of theengine in-cylinder combustion and aftertreatment components.

Those skilled in the art will recognize that, during the first fewengine cycles, there may be a delay in the accuracy of the measuredtemperature and pressure data. Due to the averaging effect, a certainamount of time may be required for the temperature and pressuremeasurements to reach steady-state. Accordingly, in order to accuratelymonitor chemical reaction status immediately after engine start-up,pressure and temperature data may be calculated using ion current data.For example, ion-based triple sensor 200 may measure an ion currentwaveform. Based on ion current waveform, ECM 130 may determine achemical reaction rate using, for example, a modified Arrheniusequation. With the determined chemical reaction rate, ECM 130 mayoperate to solve for at least one of a transient pressure value and attransient temperature value, from a set of equations. Transient pressureand transient temperature refer to pressure and temperature datacalculated by ECM 130, based on a chemical reaction rate derived withion current intensity measurements. Transient temperature and transientpressure are used primarily during the first few engine cycles, whentemperature and pressure sensors are unable to accurately detectsteady-state temperature and pressure values. In contrast, steady-statetemperature and steady-state pressure refer to temperature and pressureonce the temperature and pressure sensors have reached steady-stateoperation, after warm-up of the engine.

Consistent with the disclosed embodiment, the set of equations mayinclude a chemical reaction rate equation, a global potential minimizerfor equilibrium, a stoichiometric chemical reaction equation, a pressureconservation equation, and a state equation, wherein the rate equationmay be defined as follows:

rate=k ₀ ·T ^(n)·exp(−E _(a) /R·T)·[A] ^(x) ·[B] ^(y)

In the equation, A and B are the two species involved in the chemicalionic non-reverse reaction, and x and y are stoichiometric coefficientfor species A and species B respectively. [] denotes concentration ofthe species, which can be determined by dividing species partialpressure by total pressure. T denotes the temperature. Other constantsin the equation include a pre-exponential factor k₀, a constant n,activation energy E_(a), and gas constant R. In the equation, thechemical reaction rate is previously determined based on the ion currentintensity measurements. Temperature and species concentrations areunknowns to be solved. Pressure may be further derived from the solvedspecies concentrations.

Unlike the measured pressure and temperature that are quasisteady-state, the solved pressure and temperature are transient andindicative of the real values at the sensor location. With thesetransient parameters, as well as the measured ion current intensity, ECM130 may determine a transient status of the chemical reaction anddiagnose possible combustion and/or aftertreatment malfunctions.

According to yet another embodiment, ECM 130 may also be configured tocompare the solved transient pressure and temperature values with themeasured steady-state pressure and temperature signals in order tovalidate that the at least one ion-based triple sensor 200 is operatingappropriately. If the differences between the transient values and thesteady-state measurements are greater than predetermined thresholds, ECM130 may determine that a fault exists in ion-based triple sensor 200.Therefore, the operation of ion-based triple sensor 200 may be validatedwith its own measurements.

ECM 130 may be coupled to and in communication with injectors and/origniters in the combustion chambers 111. Based on the multiplecharacteristic parameters provided by the at least one ion-based triplesensor 200, together with other input received by ECM 130 including,among other things, engine speed, engine load, emissions production oroutput, and engine fuel consumption rate, ECM 130 may direct a controlcurrent to each injector and/or igniter to adjust the injection and/orignition timing, injection mode (with or without pilot), and injectionquality.

An indication device 140 may be operatively coupled to ECM 130, andconfigured to provide a warning signal indicative of malfunctions ofengine combustion system 10 and/or at least one ion-based triple sensor200. For instance, indication device 140 may include any componentconfigured to provide a warning signal to an operator of enginecombustion system 10. Non-limiting examples of indication device 140 mayinclude a visual device (e.g., warning lamp, LCD display, LED lamp,etc.); an audible device (e.g., speaker, bell, chime, etc.); a wirelessdevice (e.g., cell phone, pager, etc.); or any other type of outputdevice.

Consistent with one embodiment of the present disclosure, indicationdevice 140 may be a display device, for example, a computer, an operatorpanel, or an LCD for displaying faults associated with engine 110 and/oraftertreatment system 120. For example, indication device 140 mayinclude a screen that displays the fault on the screen. The fault noticemay be displayed as a diagrammatic chart including a configuration ofthe engine combustion system 10, with graphic views of engine andaftertreatment components as well as the at least one ion-based triplesensor. Faulty components may be illuminated, highlighted, or otherwisemarked in a notable manner.

FIG. 2 provides a diagrammatic illustration of an ion-based triplesensor, in accordance with an exemplary embodiment of the presentdisclosure. As illustrated in FIG. 2, ion-based triple sensor 200 mayinclude, among other things, an ion sensing unit 210, a pressure sensingunit 220, a temperature sensing unit 230, and a signal processing unit240 coupled to each sensing unit.

Ion sensing unit 210 may include a metal wire (not shown) with anexposed portion not covered with an insulating material, and aninsulation component 211 that insulates ion sensing unit 210 from otherparts of ion-based triple sensor 200. Ion sensing unit 210 may beconfigured to detect a variation in current at the metal wire byapplying a predetermined voltage thereto wherein the exposed portion isarranged in the combustion chamber as a heat-sensitive portion. The fastresponse of ion sensing unit 210 makes it capable of capturing transientionic current surge. For example, ion sensing unit 210 may detect anengine shock immediately after it initiates in combustion chambers 111.

Pressure sensing unit 220 and temperature sensing unit 230 may includerespective pressure and temperature sensing devices known to thoseskilled in the art. Pressure sensing unit 220 and temperature sensingunit 230 may be compactly integrated with ion sensing unit 210 such thatthe size of ion-based triple sensor is minimized. Furthermore, the threesensing units may be carefully positioned and shielded from each othersuch that the signal interference among the three units is eliminated.

Signal processing unit 240 may include an ion signal processingcomponent coupled to ion sensing unit 210, a pressure processingcomponent coupled to pressure sensing unit 220, and a temperatureprocessing component coupled to pressure sensing unit 220. The ionsignal processing unit may include an amplifier 212, a high-pass filter213, and a high frequency data acquisition (DAQ) unit 214. Ion currentis typically in the range of several micro-amperes to hundreds ofmicro-amperes. Therefore, the ion current signal acquired by ion sensingunit 210 may be amplified by amplifier 212. The oscillating signalportion in the ion current that corresponds to an abnormal reactionstatus is usually high-frequency. In order to extract the high frequencyportion of the signal, the amplified signal may be fed into high-passfilter 213. Accordingly, high frequency DAQ 214 may be configured tosample the filtered ion current signal at a high frequency.

The pressure signal processing unit may include a signal conditioner221, a band-pass filter 222, and a low frequency data acquisition (DAQ)unit 223. Signal conditioner 221 may be configured to reduce noises andabnormal spikes in the pressure signal acquired by pressure sensing unit210. The pressure signal may then be fed into band-pass filter 222,where the extremely low frequency and extremely high frequency portionsare removed. The filtering process may have an equivalent effect asaveraging and the filtered pressure measurement becomes quasisteady-state. Low frequency DAQ 214 may be configured to sample thefiltered pressure signal at a low frequency.

Similar to the pressure sensing unit, the temperature signal processingunit may include a signal conditioner 231, a low-pass filter 232, and alow frequency data acquisition (DAQ) unit 233. The conditionedtemperature signal may be fed into low-pass filter 232, where the highfrequency portion of the signal may be removed, and then sampled at alow frequency. Signal processing unit 240 may be operatively coupled toECM 130 and configured to transmit the sampled ion current signal,pressure signal and temperature signal to ECM 130.

INDUSTRIAL APPLICABILITY

Although the disclosed embodiments are described in association with acombustion engine and its aftertreatment system, the disclosed triplesensor may be used in any environment where it may be desirable tomonitor the status of a chemical reaction. Specifically, the disclosedtriple sensor may measure an ion current intensity, a pressure and atemperature in a chamber where a chemical reaction is taking place, anddetermine a status of the chemical reaction based on the measurements.Moreover, the disclosed triple sensor may be configured to provideindications when a fault is detected. In addition, the disclosed triplesensor may perform self-validations based on the measured signals.

FIG. 3 provides a flowchart of an exemplary combustion fault detectionprocess 300 of an ion-based triple sensor 200, in accordance with theembodiment of the present disclosure. Process 300 may include measuringan ion current intensity signal, a pressure signal and a temperaturesignal (Step 301). The measurement may be performed as early as withinthe first engine cycle. The ion signal may include information of an ioncurrent surge, which may be indicative of a shock incidence in thecombustion chamber or aftertreatment components.

Process 300 may further determine an inherent response difference amongthe three measurements (Step 302). For example, the inherent responsedifference may be high ion current with low pressure and lowtemperature, or high ion current with high pressure and low temperature.Based on the inherent response difference, process 300 may determine achemical reaction status (Step 303) and determine accordingly whether anengine or aftertreatment component fault exists (Step 304). For example,an inherent response difference of high ion current with low pressureand low temperature may correspond to an early stage combustion shockfault.

If a fault is detected, process 300 may further indicate the fault to auser of the machine (Step 305). The indication may be in the form of awarning signal or, alternatively, a fault display on a screen. Servicesuggestions to eliminate the fault may also be included with theindication. Process 300 may also adjust engine control parameters basedon the chemical reaction status to improve combustion (Step 306).Examples of engine control parameters may include injection and/orignition timing, injection mode, and injection quality. Engine controlin step 306 may involve shutting down the engine for trouble-shootingresponsive to a fatal fault. If no fault is detected (Step 304: No),process 300 may repeat Steps 301-304 to continuously monitor thechemical reaction status.

For example, process 300 may be used to detect the backfire inside thetailpipe or at the tailpipe exit. Due to extensive convective heat lossalong the length of exhaust piping system, the heat generated bybackfire may not cause immediate temperature or pressure increase, butthe ion intensity may be easily detected. ECM 130 may execute process300 to perform a diagnosis based on the inherent response differencebetween the ion current intensity signal and the temperature signal. Ifa backfire is detected, process 300 may determine control strategies tomitigate or eliminate the backfire.

FIG. 4 provides a flowchart of another exemplary combustion faultdetection and self-validation process 400 of an ion-based triple sensor,in accordance with the embodiment of the present disclosure. Process 400may measure a transient ion current waveform (Step 401). Based on thetemporal ion signal, a reaction rate may be determined (Step 402). Thetransient pressure and temperature may be solved, from a set ofequations including a chemical reaction rate equation, a globalpotential minimizer for equilibrium, a stoichiometric chemical reactionequation, a pressure conservation equation, and a state equation (Step403). With the solved pressure and temperature, as well as the measuredion current intensity, process 400 may determine a transient status ofthe chemical reaction and diagnose possible transient malfunctions inany combustion and/or aftertreatment components (Step 404). If a faultis detected, process 400 may further indicate the fault and step 406 toperform engine controls (Step 405), similar to Steps 305 and 306disclosed in FIG. 3.

Parallel to combustion fault detection Steps 405-406, process 400 mayalso measure steady-state pressure and temperature signals (Step 407).The measured steady-state pressure and temperature signals may becompared to the solved transient pressure and temperature (Step 408).Process 400 may further validate the operation of ion-based triplesensor 200 based on the comparison differences (Step 409). If a sensorfault is found (Step 409: Yes), process 400 may report the sensor faultto the user of the machine and operate ECM 130 to perform necessaryprotection actions (Step 410). If no fault is detected (Step 409: No),process 400 may repeat Steps 407-409 to continuously monitor theoperation of ion-based triple sensor 200.

Ion-based triple sensor 200 and corresponding combustion controlstrategies in the present disclosure may provide timely feedback to ECM130 as early as the first engine cycle. The sensor measurements mayindicate engine or aftertreatment component faults immediately after thecombustion process starts. Based on sensor measurements, ECM 130 maytimely adjust control parameters, for example, injection timing, modeand quantity, to regulate and optimize the combustion process.Therefore, the disclosed ion-based triple sensor 200 and correspondingcontrol strategies may serve as diagnostic tools to prevent catastrophicevents from occurring in the combustion chamber. Moreover, ion-basedtriple sensor 200 and associated control strategies may further serve asresearch tools to improve engine combustion research. For example, thecharacteristic parameters measured during the early stages of enginecombustion may provide valuable information to improve the injectiontiming, injection quantity, multi-pulse injection, spark timing, sparkduration for better engine performance and emission.

Furthermore, ion-based triple sensor 200 may compactly integrate ionsensing unit 210, pressure sensing unit 220, and temperature sensingunit 230 without interference. Therefore, the sensor may accuratelymeasure the three characteristic parameters at the same location. Inaddition, ion-based triple sensor 200 may provide improved reliabilitydue to its self-validation functions.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed ion-basedtriple sensor and corresponding control strategies without departingfrom the scope of the disclosure. Other embodiments of the presentdisclosure will be apparent to those skilled in the art fromconsideration of the specification and practice of the presentdisclosure. It is intended that the specification and examples beconsidered as exemplary only, with a true scope of the presentdisclosure being indicated by the following claims and theirequivalents.

1. An engine diagnostic method, comprising: acquiring an ionic currentintensity signal, a pressure signal and a temperature signal in acombustion chamber of an engine; determining an inherent responsedifference based on the acquired signals; determining a chemicalreaction status in the combustion chamber, based on the inherentresponse difference; and detecting an engine fault if the chemicalreaction status is outside of a threshold range.
 2. The method of claim1, further including acquiring an ionic current intensity signal, apressure signal and a temperature signal in an aftertreatment component.3. The method of claim 1, further including high-pass filtering theionic current intensity signal and low-pass filtering at least one ofthe pressure signal and temperature signal.
 4. The method of claim 1,further including: calculating a transient pressure value and atransient temperature value; and determining the chemical reactionstatus in the combustion chamber, based on at least one of the transientpressure and temperature values.
 5. The method of claim 4, whereincalculating includes: acquiring a transient ionic current waveform;deriving a chemical reaction rate in the combustion chamber of theengine, based on the acquired ionic current waveform; and solving forthe transient pressure value and the transient temperature value from aset of equations.
 6. The method of claim 5, wherein the set of equationsinclude at least two of: a chemical reaction rate equation with thederived chemical reaction rate plugged in; a global potential minimizerfor equilibrium; a stoichiometric chemical reaction equation; a pressureconservation equation; and a state equation.
 7. The method of claim 4,wherein detecting an engine fault includes detecting the engine faultbased on the at least one of the transient pressure and temperaturevalues.
 8. The method of claim 1, further including adjusting one ormore engine control parameters based on the determined chemical reactionstatus and a desired chemical reaction status.
 9. An ion-based triplesensor self-validation method, comprising: acquiring an ionic currentwaveform; calculating at least one of a transient pressure value and atransient temperature value, based on the ionic current waveform;acquiring at least one of a steady-state pressure signal and asteady-state temperature signal; comparing the at least one transientvalue with a corresponding steady-state measurement; and detecting afault associated with the ion-based triple sensor if the differencebetween the transient value and the corresponding steady-statemeasurement is outside of a threshold range.
 10. The method of claim 9,wherein the step of calculating includes: deriving a chemical reactionrate in the combustion chamber of the engine, based on the ionic currentwaveform; and solving for at least one of the transient pressure valueand the transient temperature value using a set of equations, whereinthe set of equations include at least two of: a chemical reaction rateequation with the derived chemical reaction rate plugged in; a globalpotential minimizer for equilibrium; a stoichiometric chemical reactionequation; a pressure conservation equation; and a state equation.